In an organic EL display device, an organic EL layer is stacked with a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer and a cathode in this order on an anode. Since the light emitting layer in the organic EL layer described above is formed from different materials for each RGB using a fine metal mask processed with high definition, the light emitting material is not formed between RGB pixels. On the other hand, since a fine metal mask is not used when forming the hole injection layer, the hole transport layer and the electron transport layer, these materials are also formed between each pixel. That is, the organic EL layer which does not use a fine metal mask other than for the light emitting layer is formed uniformly over the entire light emitting region of a display. Since the organic layer which forms the organic EL layer has low adhesion, a sheet on an element side where a TFT circuit or the like is formed and a sheet on a sealing plate side opposite the sheet on the element side easily peel with the organic EL layer as a boundary, and there is a problem whereby durability against physical stimulation is poor.
In addition, attempts have been made to improve adhesion by forming the entire layer of the organic EL layer using a fine metal mask, arranging an area where the organic EL layer is not deposited on a bank, and contacting a layer formed in an upper layer than the organic EL layer, for example, a sealing film and a bank surface. However, since the adhesion between the bank which is a resin material and the sealing film which is a silicon-based inorganic film is not very high, it is difficult to maintain sufficient strength.
In order to solve this problem, a technique has been disclosed (for example, Japanese Laid Open Patent Application No. 2010-103374) in which a hole injection layer is formed from a mixture of molybdenum oxide and tungsten oxide, hole injection performance and the flatness of the hole injection layer surface are improved, and it possible to manufacture an organic EL element having a low drive voltage and high light emission efficiency thereby making it easy to increase the size and achieve mass production of the organic EL element.